1. Field of the Invention
This invention is concerned with the wire sawing method for such reinforced concrete structures as buildings, dams, bridge piers, foundations and others.
2. Description of the Prior Art
Conventionally, disk blade type cutting machines equipped with circumferential blades have been widely used for cutting reinforced concrete structures. However, these cutting machines have the disadvantage that, due to various circumstance of the manufacture of blades, workability, handling and the like, the adoption of the method to large size operations is impossible. Therefore, the cutting capacity of these machines is poor, the cross-sectional area to be cut is limited to a narrow range, and also the potential depth of cut is limited to about 30-40 cm at maximum.
In addition, when submerged reinforced concrete structures are cut using disk blade type cutters, the cutters must be operated by underwater drives and it is a large burden on the workers. In addition, there are the problems such that the work efficiency is low and the diving works for long hours are dangerous. Moreover, these problems become more serious as the water depth increases.
Thereupon, this inventor has previously developed a wire sawing technique for reinforced concrete structures, in which an endless cable for cutting is laid on the reinforced concrete structures and circularly run while the running speed and tension are adjusted by a cable driving machine.
In this case, beads having a diamond abrasive layer on their surfaces are arranged on a wire rope composed of steel strands at a suitable pitch, with or without coil spring spacers, to form the cutting cable. The running speed of a cable for cutting in ordinary wire sawing is about 15-30 m/s, the tension of the stretched cable is about 50-150 kg, and the length of the cable for cutting varies according to the size of the place to be cut in reinforced concrete structures and the relative positions of the place to be cut, but usually it is about 10-60 m.
In this wire sawing technique for use in underwater cutting of reinforced concrete structures, for which safe and efficient cutting work has been regarded a difficult in the past, as well as the ordinary cutting of reinforced concrete structures on the ground, the cutting operation, even of internal reinforcing bars, can be carried out without being restricted by the crosssectional area to be cut, the depth of cut and so on, at an extremely fast cutting speed, with good workability and safely. In addition, the cutting operation is conducted in such a way that the effect to the external environment due to vibration and noise is very small.
However, in the above previous wire sawing technique, in the case of underwater cutting, the cable is subjected to large viscous resistance and form drag through the water. Consequently, there is a problem that the cutting force of the running cable is reduced. The required power output of a cable driving machine in ordinary wire sawing technique was about 37-52 hp. But in the case of underwater cutting, a greater power output was required, if possible, 80-100 hp.
Further, with the cutting force of the running cable reduced, there was a problem that in the slackening portion of the cable (the side leaving the cable diving machine) particularly when accompanied by irregular wave motion of the water, and at the same time, irregular intermittent motion in the movement of the cable driving machine, wire sawing was inconsistent.
In order to solve the above various problems, the power output of the cable driving machine was increased to the required level, for example, by mounting a large prime mover of 80-100 hp on the cable driving machine, the total weight of the installation exceeds 1 ton, and probably becomes about 1.3-1.5 tons. Accordingly, another problem arises in that the transportation, lifting and lowering, installation, movement and all other workings of the machine is more difficult. Because mobility is required in order to cut or partially dismantle various reinforced concrete structures by wire sawing, the increase of the weight and size of the cable driving machines is not desirable.
The objective of this invention is to provide a wire sawing method for reinforced concrete structures, which facilitates easier transportation, lifting and lowering of the cable driving machine and which can ensure sufficient driving power for the running cable, not only while cutting on the ground, but also while cutting reinforced concrete structures underwater.